Subject: [PATCH 4/4] at91 : implement the standby function for pm/cpuidle

From: [email-masked] (Ryan Mallon)
Date: Thu, 19 Jan 2012 09:08:40 +1100

On 18/01/12 10:40, Daniel Lezcano wrote:

> This patch groups the self-refresh on/cpu_do_idle/self-refresh off into
> a single 'standby' function.
> 
> The standby routine for rm9200 has been turned into an asm routine to have
> a better control of the self refresh and to prevent a memory access when
> running this code.
> 
> Draining the write buffer is done automatically when switching for the self
> refresh on sam9, so the instruction is added to the rm9200 only.
> 
> Signed-off-by: Daniel Lezcano <[email-masked]>

I don't think is an improvement. Russell's suggestion was to convert the
pm operations into a structure, like:

struct at91_pm_ops {
	u32  (*sdram_selfrefresh_enable)(void);
	void (*sdram_selfrefresh_disable)(u32 saved_lpr);
};

This structure should be integrated into soc.h. Note that at91_init_soc
is __initdata, so you can't use that directly, but the basic principle
is the same.

>>From there, move the pm functions for each platform to their respective
core file. For example, move the at91rm9200 functions to at91rm9200.c,
something like this:

#ifdef CONFIG_PM
static u32 at91rm9200_sdram_selfrefresh_enable(void)
{
        u32 saved_lpr = at91_sys_read(AT91_SDRAMC_LPR);

        at91_sys_write(AT91_SDRAMC_LPR, 0);
        at91_sys_write(AT91_SDRAMC_SRR, 1);
        return saved_lpr;
}

static void at91rm9200_sdram_selfrefresh_disable(u32 saved_lpr)
{
	at91_sys_write(AT91_SDRAMC_LPR, saved_lpr);
}

static struct at91_pm_ops at91rm9200_pm_ops = {
	.sdram_selfrefresh_enable  = at91rm9200_selfrefresh_enable,
	.sdram_selfrefresh_disable = at91rm9200_selfrefresh_disable,
};
#endif /* CONFIG_PM */

Then register at91rm9200_pm_ops structure some way similar to how the
at91_init_soc is done. This will mean that the pm ops for all of the
at91 platforms can be compiled into a single kernel without all of the
ifdef crud.

Thanks,
~Ryan

> ---
>  arch/arm/mach-at91/cpuidle.c |   11 ++-----
>  arch/arm/mach-at91/pm.c      |   12 +-------
>  arch/arm/mach-at91/pm.h      |   62 ++++++++++++++++++++++++-----------------
>  3 files changed, 40 insertions(+), 45 deletions(-)
> 
> diff --git a/arch/arm/mach-at91/cpuidle.c b/arch/arm/mach-at91/cpuidle.c
> index a851e6c..555d956 100644
> --- a/arch/arm/mach-at91/cpuidle.c
> +++ b/arch/arm/mach-at91/cpuidle.c
> @@ -39,20 +39,15 @@ static int at91_enter_idle(struct cpuidle_device *dev,
>  {
>  	struct timeval before, after;
>  	int idle_time;
> -	u32 saved_lpr;
>  
>  	local_irq_disable();
>  	do_gettimeofday(&before);
>  	if (index == 0)
>  		/* Wait for interrupt state */
>  		cpu_do_idle();
> -	else if (index == 1) {
> -		asm("b 1f; .align 5; 1:");
> -		asm("mcr p15, 0, r0, c7, c10, 4");	/* drain write buffer */
> -		saved_lpr = sdram_selfrefresh_enable();
> -		cpu_do_idle();
> -		sdram_selfrefresh_disable(saved_lpr);
> -	}
> +	else if (index == 1)
> +		at91_standby();
> +
>  	do_gettimeofday(&after);
>  	local_irq_enable();
>  	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
> index acf32c7..94acc12 100644
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -208,7 +208,6 @@ extern u32 at91_slow_clock_sz;
>  
>  static int at91_pm_enter(suspend_state_t state)
>  {
> -	u32 saved_lpr;
>  	at91_gpio_suspend();
>  	at91_irq_suspend();
>  
> @@ -264,16 +263,7 @@ static int at91_pm_enter(suspend_state_t state)
>  			 * For ARM 926 based chips, this requirement is weaker
>  			 * as at91sam9 can access a RAM in self-refresh mode.
>  			 */
> -			asm volatile (	"mov r0, #0\n\t"
> -					"b 1f\n\t"
> -					".align 5\n\t"
> -					"1: mcr p15, 0, r0, c7, c10, 4\n\t"
> -					: /* no output */
> -					: /* no input */
> -					: "r0");
> -			saved_lpr = sdram_selfrefresh_enable();
> -			cpu_do_idle();
> -			sdram_selfrefresh_disable(saved_lpr);
> +			at91_standby();
>  			break;
>  
>  		case PM_SUSPEND_ON:
> diff --git a/arch/arm/mach-at91/pm.h b/arch/arm/mach-at91/pm.h
> index 624c99c..b451822 100644
> --- a/arch/arm/mach-at91/pm.h
> +++ b/arch/arm/mach-at91/pm.h
> @@ -24,22 +24,31 @@
>   * still in self-refresh is "not recommended", but seems to work.
>   */
>  
> -static inline u32 sdram_selfrefresh_enable(void)
> +static inline void at91rm9200_standby(void)
>  {
> -	u32 saved_lpr = at91_sys_read(AT91_SDRAMC_LPR);
>  
> -	at91_sys_write(AT91_SDRAMC_LPR, 0);
> -	at91_sys_write(AT91_SDRAMC_SRR, 1);
> -	return saved_lpr;
> +	u32 lpr = at91_sys_read(AT91_SDRAMC_LPR);
> +
> +	asm volatile(
> +		"b    1f\n\t"
> +		".align    5\n\t"
> +		"1:  mcr    p15, 0, %0, c7, c10, 4\n\t"
> +		"    str    %0, [%1, %2]\n\t"
> +		"    str    %3, [%1, %4]\n\t"
> +		"    mcr    p15, 0, %0, c7, c0, 4\n\t"
> +		"    str    %5, [%1, %2]"
> +		:
> +		: "r" (0), "r" (AT91_BASE_SYS), "r" (AT91_SDRAMC_LPR),
> +		  "r" (1), "r" (AT91_SDRAMC_SRR),
> +		  "r" (lpr));
>  }
>  
> -#define sdram_selfrefresh_disable(saved_lpr) \
> -	at91_sys_write(AT91_SDRAMC_LPR, saved_lpr)
> +#define at91_standby at91rm9200_standby
>  
>  #elif defined(CONFIG_ARCH_AT91CAP9)
>  #include <mach/at91cap9_ddrsdr.h>
>  
> -static inline u32 sdram_selfrefresh_enable(void)
> +static inline void at91cap9_standby(void)
>  {
>  	u32 saved_lpr, lpr;
>  
> @@ -48,11 +57,13 @@ static inline u32 sdram_selfrefresh_enable(void)
>  	lpr = saved_lpr & ~AT91_DDRSDRC_LPCB;
>  	at91_ramc_write(0, AT91_DDRSDRC_LPR, lpr |
>  			AT91_DDRSDRC_LPCB_SELF_REFRESH);
> -	return saved_lpr;
> +
> +	cpu_do_idle();
> +
> +	at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr);
>  }
>  
> -#define sdram_selfrefresh_disable(saved_lpr) \
> -	at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr)
> +#define at91_standby at91cap9_standby
>  
>  #elif defined(CONFIG_ARCH_AT91SAM9G45)
>  #include <mach/at91sam9_ddrsdr.h>
> @@ -60,14 +71,12 @@ static inline u32 sdram_selfrefresh_enable(void)
>  /* We manage both DDRAM/SDRAM controllers, we need more than one value to
>   * remember.
>   */
> -static u32 saved_lpr1;
> -
> -static inline u32 sdram_selfrefresh_enable(void)
> +static inline void at91sam9g45_standby(void)
>  {
> -	/* Those tow values allow us to delay self-refresh activation
> +	/* Those two values allow us to delay self-refresh activation
>  	 * to the maximum. */
>  	u32 lpr0, lpr1;
> -	u32 saved_lpr0;
> +	u32 saved_lpr0, saved_lpr1;
>  
>  	saved_lpr1 = at91_ramc_read(1, AT91_DDRSDRC_LPR);
>  	lpr1 = saved_lpr1 & ~AT91_DDRSDRC_LPCB;
> @@ -81,14 +90,13 @@ static inline u32 sdram_selfrefresh_enable(void)
>  	at91_ramc_write(0, AT91_DDRSDRC_LPR, lpr0);
>  	at91_ramc_write(1, AT91_DDRSDRC_LPR, lpr1);
>  
> -	return saved_lpr0;
> +	cpu_do_idle();
> +
> +	at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr0);
> +	at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1);
>  }
>  
> -#define sdram_selfrefresh_disable(saved_lpr0)	\
> -	do { \
> -		at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr0); \
> -		at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1); \
> -	} while (0)
> +#define at91_standby at91sam9g45_standby
>  
>  #else
>  #include <mach/at91sam9_sdramc.h>
> @@ -101,7 +109,7 @@ static inline u32 sdram_selfrefresh_enable(void)
>  #warning Assuming EB1 SDRAM controller is *NOT* used
>  #endif
>  
> -static inline u32 sdram_selfrefresh_enable(void)
> +static inline void at91sam9_standby(void)
>  {
>  	u32 saved_lpr, lpr;
>  
> @@ -110,11 +118,13 @@ static inline u32 sdram_selfrefresh_enable(void)
>  	lpr = saved_lpr & ~AT91_SDRAMC_LPCB;
>  	at91_ramc_write(0, AT91_SDRAMC_LPR, lpr |
>  			AT91_SDRAMC_LPCB_SELF_REFRESH);
> -	return saved_lpr;
> -}
>  
> -#define sdram_selfrefresh_disable(saved_lpr) \
> +	cpu_do_idle();
> +
>  	at91_ramc_write(0, AT91_SDRAMC_LPR, saved_lpr)
> +}
> +
> +#define at91_standby at91sam9_standby
>  
>  #endif
>